2010 Escape A/C intermittent.

2010 Escape, 96K, A/C blow cool air Intermittent, I am wondering if it is electrical problem, or senser problem or else,
Observation:1. when ambient temp is cooler, A/C working fine and blowing cool air in, when ambient temp is high, only hot air was blown.

2. I could feel the A/C compressor not kick in under high ambient temp. As soon as compress started (during idol, I could tell from engine RPM changes), the cool air was blown in.

3. There was a smell when cool air starts blowing.

Any advice is welcom